1. Field of the Invention
The present invention relates to a method and apparatus comprising an improved gas-liquid contact media. This invention has particular utility in the treatment of wastewater by biological oxidation.
2. Background and Description of the Related Art
The biological oxidation of organic pollutants in wastewater by passage over a gas-liquid contact media is a well established method of sewage treatment. The wastewater is applied to the media and allowed to uniformly disperse over the media surface. Bacteria which are present in the wastewater are encouraged to cling to and propagate upon the media surface when an adequate amount of oxygen is brought into direct contact with the bacteria. This oxygen is most often supplied in the form of air.
Most treatment surfaces are constructed so as to have vertical planar surfaces. This arrangement allows the wastewater to flow downward over the media surface by gravity in a falling film. Air, the oxygen-containing gas, is either flowing countercurrently to the falling film or concurrently, depending on the design of the treatment facility.
These biological oxidation gas-liquid contact media surfaces are commonly referred to as trickling filters by those skilled in the art. Initial trickling filter designs employed coarse rocks as bulk surface area. These rock trickling filters have numerous disadvantages as will become apparent later in this document. Presently, most trickling filters are molded from plastic sheet material. Plastic media provides large amounts of surface area thus enabling greater treatment area per unit of volume. Hence, treatment facilities of a given capacity can utilize a much smaller portion of the facility dedicated solely to trickling filters. This is important as the trickling filter is only one portion of complete sewage treatment.
Prior trickling filters have numerous shortcomings. Generally, all previous trickling filters constructed from plastic materials consisted of a flat sheet of plastic attached to another formed sheet of a folded or raised surface shape. These sheets are attached together by glue or other attachment methods to form a three-dimensional unit with hollow channels extending lengthwise or diagonal to the media unit.
Treatment media constructed with diagonal channels have the distinct disadvantage that the wastewater will not contact the undersides of the diagonal channels in this media design. This results in a substantial loss of total treatment surface that has no contact with the wastewater. This lack of underside wetting action is also experienced with traditional rock trickling filters. Further, rock filters restrict flow and tend to become clogged with biomass if used over extended time periods.
Additional disadvantages of existing media configurations are geometric designs that utilize open vertical channels that are unobstructed throughout their vertical axis. This allows wastewater to enter at the top of the channel as it drips off the sheet above and avoid any contact with the surface of the media thus precluding the treatment action of the bacteria residing on the media surface (biomass). The untreated wastewater is thus discharged with a portion of wastewater that has made contact with the treatment surface and dilutes the performance of the treatment process as a whole.